AIT Chapter 5 Sensor Networks
Questions about the lecture 'Advanced Internet Technology' of the RWTH Aachen Chapter 5 Sensor Networks
Questions about the lecture 'Advanced Internet Technology' of the RWTH Aachen Chapter 5 Sensor Networks
Kartei Details
| Karten | 173 |
|---|---|
| Sprache | English |
| Kategorie | Informatik |
| Stufe | Universität |
| Erstellt / Aktualisiert | 05.02.2017 / 26.02.2017 |
| Weblink |
https://card2brain.ch/box/20170205_ait_chapter_5_sensor_networks
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| Einbinden |
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How does it works?
[ToA.trilateration.localization.protocols.WSN.sensor networks, 2]
1. Receive signal measuring ttrans, vprop and tarrival
2. Compute distance d
What are the characteristics?
[ToA.trilateration.localization.protocols.WSN.sensor networks, 2]
1. Exact time synchronization required
2. Use round-trip time of signal // Two-way ToA
How does it works?
[TDoA.trilateration.localization.protocols.WSN.sensor networks, 3]
1. Send two signals with different vprop // E.g. use ultrasound and radio
2. Receive signals measuring different tarrival
3. Compute distance d
What are the characteristics?
[TDoA.trilateration.localization.protocols.WSN.sensor networks, 2]
1. Expensive and energy-intensive HW required
2. Use global positioning system (GPS)
What are the characteristics?
[GPS.TDoA.trilateration.localization.protocols.WSN.sensor networks, 3]
1. 32 satellites 20.000km above ground
2. Satellites broadcast ID and time reference
3. 4 broadcasts necessary for localization
4. For WSNs no GPS receivers but deploy nodes
How does it works?
[math.trilateration.localization.protocols.WSN.sensor networks, 3]
1. Input with (xi,yi) coordinates of anchor point i, ri distance to anchor i
2. Goal is to get (xu,yu) unknown coordinates of node
3. Solve system of equations via Pythagoras
What are the equations and its variations?
[math.trilateration.localization.protocols.WSN.sensor networks, 3]
1. (xi-xu)² + (yi-yu)² = ri² for three nodes
2. Subtract third from first and second
3. Rearrange to linear equation for unknowns
2[x3-x1,y3-y1;x3-x2,y3-y2] * [xu,yu] = [(r1²-r3²)-(x1²-x3²)-(y1²-y3²);(r2²-r3²)-(x2²-x3²)-(y2²-y3²)]
What holds for inaccurate distances?
[math.trilateration.localization.protocols.WSN.sensor networks, 2]
1. If only ri0 = ri+epsi available
2. Then use several anchors for over-determined system, minimizing mean square error
What holds for lonely nodes (<3anchors)?
[math.trilateration.localization.protocols.WSN.sensor networks, 3]
1. If nodes can not hear up to 3 anchors
2. Then spread position knowledge over simple nodes
3. But handle accumulated errors
What is the idea?
[triangulation.localization.protocols.WSN.sensor networks]
Use angle for position estimates
What are different techniques for directional antennas?
[triangulation.localization.protocols.WSN.sensor networks, 2]
1. On node
2. On special nodes
How does it works?
[on node.triangulation.localization.protocols.WSN.sensor networks, 2]
1. Mechanically rotate or 2. electrically steerable
How does it works?
[on special node.triangulation.localization.protocols.WSN.sensor networks, 2]
1. Rotate at different offsets
2. Time between control frames yield angles
